Smart grids turn to wireless systems

As one of the very few smart metering providers, Kamstrup A/S (Skanderborg, Denmark) offers RF-communication in their smart metering system and has done so for more than ten years. Seen from Kamstrup’s point of view, the reason why wireless systems prevail in smart grid technology is simple: RF works – a plain fact which is being corroborated by numerous, high-performing RF-based systems from all over the world.

In the past, Kamstrup offered RF and PLC solutions together, but has now terminated its PLC program as RF very soon began to show much more convincing results. The evidence is plenty.

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Sweden was one of the first countries to roll out smart meters nationwide, and now the Swedish case study offers experience to learn from. Many utilities who first opted for a PLC solution have afterwards switched to an RF-solution as PLC showed poor performance on meter readings, of which 60 to 90 percent was traceable to grid disturbances. Some have chosen to mend the problem by installing expensive filters. Some PLC providers therefore take reservations against grid disturbances when guaranteeing 100 percent performance claiming disturbances to be a separate problem to be dealt with and thus pushing it back to the utility. But the fact is that cables are simply a hard environment for communication. The increased disturbance level in the grid which caused many PLC networks to fail in Sweden could for a large part be traced to the massive exchange of incandescent light-bulbs with low-energy light bulbs.

All electric devices which are connected to the grid are also potential sources of grid disturbance as they not only consume power from the grid, but also return electromagnetic disturbances. The Electromagnetic Compatibility-directive (EMC) regulates how much disturbance electric devices may cause. But even though the equipment which is now causing problems in Sweden may comply with the EMC-directive, it is still liable to influence a PLC-based meter reading system because the communication unit in the meter is affected by the total amount of disturbances generated by all installed equipment in a house. So, when substantial changes happen simultaneously – like the out-phasing of the incandescent light bulb – the meter reading system can be affected in spite of the regulatory fulfillments of the individual product. With the Smart Grid ahead such substantial changes will be even more frequent.